Abstract
The surface impedance of two 350nm thick YBCO films was measured for temperatures between 4.2K and 150K in a copper cavity at 87 GHz. Both films, one grown by electron beam evaporation on MgO, the other one by high oxygen-pressure dc sputtering from a stoichiometric target on LaAlO3, provide critical temperatures of about 91K, low residual surface resistances of Rs(4.2K) < 1mΩ and low specific resistivities in the normal state of ϱ(100K) < 85μΩcm. The experimental data obtained on these two films are compared to a d-wave model of superconductivity which incorporates elastic and inelastic scattering. Good agreement between theory and the experimental results for both the surface resistance and the penetration depth in the whole temperature range is achieved for scattering phase shifts near 0.4π and order parameter amplitudes in the range of 2Δ0(0)/kBTc = 6.0 – 7.5 without subtracting an extrinsic residual surface resistance.
Published Version
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